In present practice, it is common to form the bow of large vessels with a spheroidal structure projecting from the lower stem forming what is commonly known as a "bulbous bow". This structure, faired into the shell plating of the hull, serves to reduce the hydrodynamic drag form of the hull and thereby reduce the energy required to propel the vessel through the water. The structure is built with sufficient strength and rigidity to withstand the normal forces of use with the customary factor of safety. These normal forces include the hydrodynamic forces of the sea as well as the impacts and pressures which might be expected in low energy collisions and contacts during docking and warping maneuvers for example.
In collisions between vessels, it has been found that a bulbous bow structure of a colliding vessel can result in increased damage to the vessel collided with. This is caused by the location of the bulbous bow, forward of the bow and below or at the waterline, and the form of the bulbous portion. The spheroidal form presents essentially a point concentration of force making the structure an excellent penetrating tool, and an extremely efficient structural shape which readily overcomes the structural resistance of the relatively flat portions of the hull of the vessel collided with penetrating deep into the hull structure of that vessel with often, no major structural damage to the bulbous portion of the bow of the colliding vessel. Two cases in point where this occurred are the collision between the Sea Witch and the Esso Brussels in New York Harbor in June of 1973 and the collision between the NOTRE DAME VICTORY and the ATHOS at Paulsboro, New Jersey in February 1974.